Screen Saver Problems?

Hi,
I have some custom screensavers/wallpapers installed on my mini SD card, and some times only half the image will show when I answers the phone and I have to go into the menu screen and back to get the full image again.This has only happened a few times, any ideas why :confused:
Thank You, tantra.

The Incoming Call screen is theme controlled and when you are on a call it's always a white screen with the # and about 1/4 of your home screen wallpaper.